The competing renewal application is for the German Clinic Center of The Environmental; Determinants of Diabetes in the Young (TEDDY) study. The primary objective of this multi-center, multi-national, epidemiological study is the identification of infectious agents, dietary factors, or other environmental exposures that are associated with increased risk of autoimmunity and type 1 diabetes mellitus (T1DM). Factors affecting specific phenotypic manifestations such as early age of onset or rate of progression, or with protection from the development of T1DM will also be identified. TEDDY is an observational cohort study in which newborns who are less than 4 months of age and have high risk HLA alleles in the general population or are first-degree relatives of patients affected with T1DM will be enrolled. Six Clinical Centers in the United States and Europe will screen 361,588 newborns of which it is anticipated that 17,804 will be eligible for enrollment with just over 7,800 followed. Recruitment stared in September of 2004 and will continue until December 31, 2009. Participants will be followed to age 15 years. Identification of such factors will lead to a better understanding of disease pathogenesis and result in new strategies to prevent, delay or reverse T1DM.